[RabbitMQ] Prevent Amqp connection when running the NestJS application in standalone

[dennis0126]

Sometimes I would like to run the NestJS application in standalone without connecting to a real RabbitMQ instance. For example, I have processes that seed the database or generate the Swagger doc, which will start the NestJS application but do not require RabbitMQ communication.

However, I found no ways to prevent connecting to RabbitMQ instance. connection.init() is called when RabbitMQModule is first created. https://github.com/golevelup/nestjs/blob/master/packages/rabbitmq/src/rabbitmq.module.ts#L84

I got the following error when trying to initialize the NestJS application.

[Nest] 23152  - 03/20/2023, 4:14:17 PM   ERROR [AmqpConnection] Disconnected from RabbitMQ broker (default)

[Nest] 23152  - 03/20/2023, 4:14:22 PM   ERROR [ExceptionHandler] Failed to connect to a RabbitMQ broker within a timeout of 5000ms

Setting registerHandlers: false does not help in this case. Is there any way that I can initialize the NestJS application without throwing error in AmqpConnection?

[nolawnchairs]

Getting the same issue when running a debugger. The connection times out and crashes

[kakui-lau]

Have you solved the same problem？

[xBajci]

I have the same use case. I'd like to start the app without the rabbit trying to connect. We are using ConfigMudule to provide rabbitmq options and if enabled is false the rabbit should not try to connect.

@Module({
  imports: [
    RabbitMQModule.forRootAsync(RabbitMQModule, {
      inject: [ConfigService],
      useFactory: async (config: ConfigService<AppConfig, true>) => {
        const rabbitMqConfig = config.get<AppConfig['rabbitmq']>('rabbitmq');

        return {
          exchanges: [
            {
              name: rabbitMqConfig.exchange,
              type: rabbitMqConfig.topic,
            },
          ],
          uri: rabbitMqConfig.uri,
          prefetchCount: rabbitMqConfig.prefetchCount,
        };
      },
    }),
  ],
  exports: [RabbitMQModule],
})
export class AmqpModule {}

What would be the best way to implement it?

One solution could be to dynamically register a custom amqp module that based on the config registers either the original rabbitMq module or a mocked module with a mocked provider. But that sounds like too much work for this simple thing.

[huantaoliu]

I have the same usecase, where I want to register rabbitmq dynamically and programatically.

Maybe we can add a flag and pass to AmqpConnectionFactory(), so it won't call init() if the flag is false. then latter onApplicationBootstrap() won't need to process any connections. That might work. I can try to put up a MR if the author thinks it's a good approach.

[underfisk]

@huantaoliu I generally like that idea, we could add a flag to skip initialization, feel free to create a PR with a proposal and I'll review it

[huantaoliu]

ok will work on that.

[LucasHang]

Perhaps this optinal config can be useful? In theory, it allows to avoid connection during bootstrap and adding the connection in another moment.